Triton Reagents, RTN-X is a specialized product from the Triton line designed to help corals recover from Rapid Tissue Necrosis (RTN) and other forms of rapid tissue deterioration in the reef aquarium. RTN is one of the most feared and devastating afflictions in the reef aquarium hobby, capable of destroying coral colonies, especially SPS (small polyp stony corals), in a matter of hours or days.